CD4 is a glycoprotein on the surface of T-cells in the human body. It is has four immunoglobulin or antibody domains, labelled D1 to D4. CD4 is of particular interest because HIV binds to CD4 on a T-cell facilitating HIV infection.
The 1CDH structure on the Protein Database shows a crystallization of domains D1 and D2 of CD4. The D1 and D2 amino-terminal domains contain the residues involved in HIV interaction.
CD4 consists primarily of beta sheets (red) connected by loops (pink). There are two small helices in the D1 and D2 domains (light blue).
Below is a model showing the surface of CD4 D1 and D2.
There are two disulfide bonds within the D1 and D2 domains between Cys16&Cys84 and Cys130&Cys159 (shown in red).
The image below shows a spacefilling model of the protein using vanderWaal's radii. Each sphere is color labelled by atom: Carbon (green), Nitrogen (blue), Oxygen (red).
All images derived from PDB structure 1CDH (DOI: 10.2210/pdb1cdh/pdb) using pyMOL.
Well done!
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